OT - help me with adding this tone control to an amp

[saxtim]

I'm about to start building a Fender Champ:

http://www.ampwares.com/ffg/schem/champ_5f1_schem.gif

I'd like to incorporate a tone control from the princeton of the same era:

http://www.ampwares.com/ffg/schem/princeton_5f2-a_schem.gif

I want to put this on a switch though so I can take it in and out of the circuit. I'm pretty sure this can be done with a 3PDT switch as such:

http://www.geocities.com/mejafu/tone_circuit.jpg

(cut and paste in new window for it to open)

If have a couple of questions though - firstly should I ground the switch as I've shown or just leave the points not connected to anything?

Is there a simplier way to do this?

Will I get a 'pop' when switching between with the tone control and without? Can in be gotten rid of?

Thanks
tim

[vdm]

very doable!

ill try to talk you through it because i cant post any pictures...

please correct me if i'm wrong but the only difference is the tone section, the presence of a bypass cap on the first triodes cathode, and an extra power supply filter cap.

I would suggest building it like the princeton, as this will give your power supply better filtering, and you could make that bypass cap switchable for what i think would be like a gain switch.

as for the tone control you'll need a dpst or dpdt to switch it in/out
the pot with two caps on it's lugs is the tone control pot - the other is the volume. the pot and two caps will need to be switched out if you want to bypass it. to do this take the lead going to the wiper of the tone pot, and put it into a switch, now run the throw pole of the switch to the pot, and do the same with the bottom (volume control side) of the cap.

it will look just like a standard (non-grounded input) effect pedal bypass except you wont jumper across the second set of lugs (doing this would set the volume to max all the time).

good luck with the build and let us know how you go with it

trent

[Peter Snowberg]

That looks great.

No need for a 3PDT as a DPDT will do just fine. You can forget about one of those lower contacts in your pic.

I like the idea of forcing the tone control to ground when bypassed. That will reduce any click to the minimum by eliminating any DC stored in the caps.

Very cool, and yes... please do let us know how it goes.

Take care,
-Peter